Component carrier with a stepped cavity and a stepped component assembly embedded within the stepped cavity

ABSTRACT

Described are component carriers including a stepped cavity into which a stepped component assembly is embedded. The component carriers have (a) fully cured electrically insulating material originating from at least one electrically insulating layer structure of the component carrier and circumferentially surrounding the stepped component assembly and/or (b) an undercut in a transition region between a narrow recess and a wide recess of the stepped cavity. Further described are methods for manufacturing such component carriers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of the EuropeanPatent Application No. 18 177 090.0 filed 11 Jun. 2018, the disclosureof which is hereby incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the present invention generally relate to the technicalfield of component carriers onto which in usual applications electroniccomponents are mounted in order to form an electronic assembly. Inparticular, embodiments of the present invention relate to a componentcarrier comprising a stepped cavity into which a stepped componentassembly is embedded and to methods for manufacturing such componentcarriers.

TECHNOLOGICAL BACKGROUND

Component carriers onto which electronic assemblies comprising severalelectronic components are built up are widely used in many electronicconsumer devices such as for instance computing devices, communicationdevices, display devices etc. This enumeration is not complete and thenumber and the type of electronic devices having electronic assembliesbuilt up at component carriers is continuously getting larger.

In order to increase the integration density of electronic assembliesthere have been developed component carriers which, in addition ofproviding mechanical support and electric connections for surface mountdevice (SMD) electronic components, provide some further functionalityby embedding components such as e.g. active or passive electroniccomponents, thermal conductive components, optical components etc.Further functionality can be added to a component carrier also byembedding a sensor device such as an optical sensor, a temperaturesensor, a gas sensor etc.

US 2012/0217049 A1 discloses a printed circuit board (PCB) having acavity into which an imaging device is embedded. The imaging devicecomprises a light receiver. The imaging device is embedded in such amanner that that the light receiver faces a first surface of a substrateof the PCB.

Embedding an imaging device or generally embedding a sensor device intoa component carrier such as a PCB is a procedure which has to be carriedout very carefully. In particular when embedding a sensor device closeto a surface of a component carrier it has to be made sure that atypically very sensitive sensing surface of the sensor device will notbe damaged e.g. when during manufacture of the component carrier thesensor device is subjected to a possibly harmful chemical or mechanicalenvironment and/or is subjected to high temperatures.

In this context it is known to temporarily protect a sensor device to beembedded with an appropriate sensor protection film. However, using suchprotection film makes the manufacture of a component carrier having anembedded component such as a sensor complex and costly.

SUMMARY

There may be a need for facilitating the manufacture of a componentcarrier having an embedded component.

This need may be met by the subject matter according to the independentclaims. Advantageous embodiments of the present invention are describedby the dependent claims.

According to a first aspect of the invention there is described a methodof manufacturing a component carrier. The described method comprises (a)providing a temporary carrier; (b) providing, attached to the temporarycarrier, an at least partially uncured electrically insulating layerstructure having a narrow recess; (c) providing a layer stack comprisingat least one electrically insulating layer structure and/or at least oneelectrically conductive layer structure, the layer stack having a widerecess; (d) arranging a stepped component assembly at least within thenarrow recess; and (e) (mechanically)connecting the at least partiallyuncured electrically insulating layer structure with the layer stack bycuring the (previously) at least partially uncured electricallyinsulating layer structure such that the stepped component assembly isarranged within a stepped cavity being defined by the narrow recess andby the wide recess.

According to a further aspect of the invention there is described acomponent carrier comprising (a) a layer stack comprising at least twoelectrically insulating layer structures and/or at least oneelectrically conductive layer structure and comprising a stepped cavitywithin the layer stack, the stepped cavity having a wide recess and anarrow recess; and (b) a stepped component assembly arranged within thestepped cavity. The stepped component assembly is substantiallycompletely circumferentially surrounded by a fully cured electricallyinsulating material originating from at least one electricallyinsulating layer structure of the at least two electrically insulatinglayer structures.

In another embodiment, a method of manufacturing a component carrierincludes providing a layer stack comprising at least one electricallyinsulating layer structure and/or at least one electrically conductivelayer structure; forming a stepped cavity within the layer stack, thestepped cavity being defined by a narrow recess and by a wide recess,wherein the wide recess is formed by inserting a non-adhesive materialin the layer stack and removing a portion of the layer stack above thenon-adhesive material; and embedding a stepped component assembly withinthe stepped cavity.

In an alternative embodiment a component carrier includes a layer stackhaving at least one electrically insulating layer structure and/or atleast one electrically conductive layer structure; a stepped cavitywithin the layer stack, the stepped cavity including a narrow recess anda wide recess; and a stepped component assembly embedded within thestepped cavity, with the stepped cavity including an undercut in atransition region between the narrow recess and the wide recess.

OVERVIEW OF EMBODIMENTS

In the context of this document, the term “component carrier” may denoteany support structure which is capable of accommodating one or more(electronic) components thereon and/or therein for providing mechanicalsupport and/or electrical connectivity. In other words, a componentcarrier may be configured as a mechanical and/or electric carrier forcomponents. Electrical conductivity is provided by conductor paths whichmay be formed at the surface of the component and/or within innerstructured electrically conductive layers of the component carrier beingrealized as a so-called multilayer component carrier.

In particular, a component carrier may be one of a Printed Circuit Board(PCB), an (organic) interposer, and an IC Integrated Circuit (IC)substrate. A component carrier may also be a hybrid board combiningdifferent ones of the above-mentioned types of component carriers.

In an embodiment, the component carrier comprises a stack of at leastone electrically insulating layer (structure) and at least oneelectrically conductive layer (structure). For example, the componentcarrier may be a laminate of the mentioned electrically insulating layerstructure(s) and electrically conductive layer structure(s), inparticular formed by applying mechanical pressure, if desired supportedby thermal energy. The mentioned stack may provide a plate-shapedcomponent carrier being capable of providing a large mounting surfacefor further components and being nevertheless very thin and compact. Theterm “layer structure” may in particular denote a continuous layer, apatterned layer or a plurality of non-consecutive islands within acommon plane.

In an embodiment, the component carrier is shaped as a plate. Thiscontributes to a compact design, wherein the component carriernevertheless provides a large basis for mounting (surface mount device,SMD) components thereon. Furthermore, in particular a naked die asexample for an embedded electronic component, can be convenientlyembedded, thanks to its small thickness, into a thin plate such as aprinted circuit board.

In an embodiment, the component carrier is configured as one of thegroup consisting of a printed circuit board, and a substrate (inparticular an IC substrate).

In this document the term “Printed Circuit Board” (PCB) may particularlydenote a component carrier which is formed by laminating severalelectrically conductive layer structures with at least one electricallyinsulating layer structure, for instance by applying pressure, ifdesired accompanied by the supply of thermal energy. A PCB may beplate-shaped (i.e. planar), three-dimensionally curved (for instancewhen manufactured using 3D printing), or may have any other shape. Aspreferred materials for PCB technology, the electrically conductivelayer structures are made of copper, whereas the electrically insulatinglayer structures may comprise resin and/or glass fibers, so-calledprepreg material or, after curing, FR4 material. The variouselectrically conductive layer structures may be connected to one anotherin a desired way by forming through-holes through the laminate, forinstance by laser drilling or mechanical drilling, and by filling themwith electrically conductive material such as in particular copper,thereby forming vias as through-hole connections. Alternatively, atleast some via connections may be realized by means of blind vias. Apartfrom one or more (electronic) components which may be embedded, a PCB isusually configured for accommodating one or more SMD components on oneor both opposing surfaces of the plate-shaped PCB. They may be connectedto the respective main surface by soldering. A dielectric part of a PCBmay be composed of resin with reinforcing fibers such as e.g. glassfibers.

In this document the term “substrate” may particularly denote a smallcomponent carrier having substantially the same size as a component (inparticular an electronic component) to be mounted thereon. Morespecifically, a substrate can be understood as a carrier for electricconnections or electric networks as well as component carrier comparableto a Printed Circuit Board (PCB), however with a considerably higherdensity of laterally and/or vertically arranged connections. Lateralconnections are, for example, conductive paths, whereas verticalconnections may be for example drill holes. These lateral and/orvertical connections are arranged within the substrate and can be usedto provide electrical and/or mechanical connections of housed componentsor unhoused components such as bare dies or semiconductor IC chips, witha PCB or intermediate PCB. The (electronic) components, in particularunhoused or bare components, may be components being embedded within thecomponent carrier. Thus, the term “substrate” may also include “ICsubstrates”. A dielectric part of a substrate may be composed of resinwith reinforcing spheres (such as glass spheres).

The described at least one electrically insulating layer structure maycomprise at least one of the group consisting of resin (such asreinforced or non-reinforced resins, for instance epoxy resin orBismaleimide-Triazine resin, more specifically FR-4 or FR-5), cyanateester, polyphenylene derivate, glass (in particular glass fibers,multi-layer glass, glass-like materials), prepreg material, polyimide,polyamide, liquid crystal polymer (LCP), epoxy-based Build-Up Film,polytetrafluoroethylene (Teflon®), a ceramic, and a metal oxide.Reinforcing materials such as webs, fibers or spheres, for example madeof glass (multilayer glass) may be used as well. Teflon® is a registeredtrademark of The Chemours Company FC of Delaware, U.S.A. Althoughprepreg or FR4 are usually preferred, other materials may be used aswell. For high frequency applications, high-frequency materials such aspolytetrafluoroethylene, liquid crystal polymer and/or cyanate esterresins may be implemented in the component carrier as electricallyinsulating layer structure.

The at least one electrically conductive layer structure may comprise atleast one of the group consisting of copper, aluminum, nickel, silver,gold, palladium, and tungsten. Although copper is usually preferred,other materials or coated versions thereof are possible as well, inparticular coated with supra-conductive material such as graphene.

A component (of the stepped component assembly) can be selected from agroup consisting of an electrically non-conductive inlay, anelectrically conductive inlay (such as a metal inlay, preferablycomprising copper or aluminum), a heat transfer unit (for example a heatpipe), an electronic component, or combinations thereof. For example,the component can be an active electronic component, a passiveelectronic component, an electronic chip, a storage device (for instancea DRAM or another data memory), a filter, an integrated circuit, asignal processing component, a power management component, anoptoelectronic interface element, a voltage converter (for example aDC/DC converter or an AC/DC converter), a cryptographic component, atransmitter and/or receiver, an electromechanical transducer, a sensor,an actuator, a microelectromechanical system (MEMS), a microprocessor, acapacitor, a resistor, an inductance, a battery, a switch, a camera, anantenna, a logic chip, and an energy harvesting unit. However, othercomponents may be embedded in the component carrier. For example, amagnetic element can be used as a component. Such a magnetic element maybe a permanent magnetic element (such as a ferromagnetic element, anantiferromagnetic element or a ferrimagnetic element, for instance aferrite core) or may be a paramagnetic element. However, the componentmay also be a further component carrier, for example in a board-in-boardconfiguration. The component may be surface mounted on the componentcarrier and/or may be embedded in an interior thereof. Moreover, alsoother components, in particular those which generate and emitelectromagnetic radiation and/or are sensitive with regard toelectromagnetic radiation propagating from an environment, may be usedas component.

The component carrier may be a laminate-type component carrier. In suchan embodiment, the component carrier is a compound of multiple layerstructures which are stacked and connected together by applying apressing force, if desired accompanied by heat.

In this document the term “at least partially uncured material”particularly denotes a material which has the property to at leastpartially melt or become flowable by the application of elevatedpressure and/or elevated temperature, and become fully hardened or cured(and thereby becomes solid) when releasing the applied elevated pressureand/or elevated temperature. Consequently, applying elevated pressureand/or elevated temperature may cause melting of the curable or at leastpartially uncured material, followed by an irreversible hardening uponreleasing the applied high pressure and/or high temperature. Inparticular, the “at least partially uncured material” may comprise orconsist of a so-called B-stage material and/or a so-called A-stagematerial. By providing a layer (structure) with resin, prepreg, or anyother B-stage material the layer (structure) may re-melt duringlamination so that resin (or the like) may flow for interconnecting thevarious elements and for closing gaps or voids and may thereforecontribute to a stable intrinsic interconnection within the componentcarrier under manufacture. Upon connecting such a structure by theapplication of pressure and/or heat, i.e. by lamination, only thelow-flow prepreg or no-flow prepreg will re-melt slightly and accomplisha local connection. Two fully cured layer structures will not establisha mutual adhesive connection, allowing to subsequently take out a piecedelimited by a circumferential milling line and a connection areabetween the two fully cured layer structures.

The described method of manufacturing a component carrier is based onthe idea that a temporary carrier being temporarily arranged at thesurface of a component carrier into which a stepped component assemblyis to be embedded can be used in beneficial manner for two purposes (A)and (B).

A first purpose (A) is to serve as a mechanical stop when inserting thestepped component assembly into the stepped cavity. Thereby, it can bemade sure that, when inserting the stepped component assembly “as deepas possible” into the stepped cavity, a front surface of the componentwill be perfectly aligned with the outer surface of the componentcarrier at which the temporary carrier is arranged. This means that thefront surface of the component and the outer surface of the componentcarrier are coplanar. Such a coplanarity may be suitable for manyapplications of embedded (electronic and/or optic) components because(i) on the one hand the component is exposed to the outside of thecomponent carrier and (ii) on the other hand the component is notprotruding from the outer surface of the component carrier.

A second purpose (B) is to serve as a (mechanical) protection during theprocedure of embedding and, if applicable, during a further processingof the component carrier with the already embedded component. This maysimplify processing because comparatively “rough” process steps can beemployed which, in the absence of the protecting temporary carrier, mayharm at least the front surface of the component of the steppedcomponent assembly.

In some embodiments the described temporary carrier may be realizedsimply as an adhesive tape. The adhesive tape may be for instance a socalled “thermo release tape” the stickiness of which can be reducedsimply by applying heat.

The step of connecting the at least partially uncured electricallyinsulating layer structure may be realized by means of a properlamination procedure by applying pressure to the entire layer structures(including the temporary carrier). Such a lamination can be supported ina known manner by thermal energy, which may cause a “melting” of thepartially uncured electrically insulating layer. During the laminationprocess the “molten” material, in particular resin, may flow around atleast one component of the stepped component assembly such that thecomponent assembly will be embedded within the component carrier in a(mechanically) smooth and reliable manner.

For the sake of clarity it is pointed out that the steps being definedwith the described method may be carried out in different sequences:

(A) In some embodiments (see e.g. FIGS. 1A to 1E) a part of the steppedcomponent assembly, namely a narrow component of the stepped componentassembly, is inserted into the narrow recess before the provided layerstack (having the wide recess) is placed next to the at least partiallyuncured electrically insulating layer structure (having the narrowrecess). With this placement of the layer stack, which placement is donebefore the final “connecting step”, the wide recess is imposed on thewide component of the stepped component assembly. This means that thestepped cavity is formed after only a part of the stepped componentassembly is arranged within the narrow recess of the later formedstepped cavity.

(B) In other embodiments (see e.g. FIGS. 2A to 2L) the stepped cavity isformed before the stepped component assembly is inserted therein. Thismeans that the layer stack having the wide recess is placed at oradjacent to the at least partially uncured electrically insulating layerstructure having a narrow recess before the stepped component assemblyis inserted into the stepped cavity. Also, in these other embodimentsthe step of connecting the at least partially uncured electricallyinsulating layer structure with the layer stack by curing the at leastpartially uncured electrically insulating layer structure is the laststep of the described method. Of course, further processing steps mayfollow.

According to a further embodiment of the invention at least oneelectrically insulating layer structure of the layer stack comprises afurther at least partially uncured electrically insulating layerstructure. This may provide the advantage that not only a first (upper)component of the stepped component assembly but also the second (lower)component of the stepped component assembly may be embedded in areliable manner. Thereby, benefit may be taken from the presence of theadditional at least partially uncured electrically insulating materialof the further at least partially uncured electrically insulating layerstructure.

According to a further embodiment of the invention the method furthercomprises, after arranging the stepped component assembly within thestepped cavity and before connecting the at least partially uncuredelectrically insulating layer structure with the layer stack, laminatingthe entire structure comprising (at least) the temporary carrier, the atleast partially uncured electrically insulating layer structure, and thelayer stack in such a manner that at least partially uncuredelectrically insulating material flows at least partially around thestepped component assembly. This may provide the advantage that alreadyduring the lamination procedure the stepped component assembly can beembedded within the stepped cavity in a mechanically smooth and reliablemanner.

In (above described) embodiments, where the layer stack also comprisesthe (at least one) further at least partially uncured electricallyinsulating layer structure the corresponding further at least partiallyuncured material may flow around the stepped component assembly. Thismeans that the overall flow of at least partially uncured electricallyinsulating material may “start from different location” such that thestepped component assembly can be embedded in a reliable manner fromboth (upper) and (lower) sides.

According to a further embodiment of the invention the method furthercomprises removing the temporary carrier from the connected structurecomprising the previously at least partially uncured electricallyinsulating layer structure and the layer stack. This may provide theadvantage that at the surface, where the temporary carrier has beenarranged, further processing of the connected structure can beaccomplished. Such a further processing may not only include appropriatesurface treatment but also a building up a further layer structure inorder to add an appropriate built-up structure which may add furtherfunctionality to the manufactured component carrier.

According to a further embodiment of the invention the method furthercomprises providing a single electrically conductive layer structurebetween (i) the temporary carrier and (ii) the at least partiallyuncured electrically insulating layer structure having the narrowrecess. Thereby, in particular the single electrically conductive layerstructure has an opening being spatially concurrent with the narrowrecess.

This embodiment may provide the advantage that after removing thetemporary carrier there will be an outer conductive layer structurewhich can be used for electrically contacting the component carrierrespectively the embedded stepped component assembly with electroniccircuitry being external to the component carrier. Thereby, appropriateconductor paths can be formed from the single electrically conductivelayer structure by means of an appropriate structuring or patterning.Further, preferably after removing the temporary carrier electricconnections to the “inside” of the component carrier and in particularto the embedded stepped component assembly can be formed by metallizingvias, which may be generated by means of known mechanical and/or laserdrilling procedures.

The described component carrier is based on the idea that a smooth andreliable embedding of the stepped component assembly can be realized byusing previously at least partially uncured electrically insulatingmaterial from an electrically insulating layer structure within whichone of the two recesses of the stepped cavity is formed. This means thatat least one of the two electrically insulating layer structures servesnot only as a structure defining one of the recesses of the steppedcavity but also as a reservoir for at least partially uncuredelectrically insulating material which, e.g. during a proper laminationprocedure, is used for embedding at least a part of the steppedcomponent assembly. Thereby, gaps, which may be formed between an outersurface of the stepped component assembly and an inner sidewall of therespective (narrow or wide) recess, may be filled with this at leastpartially uncured material, which will later be cured e.g. by releasingpressure and/or by lowering the temperature.

Filling such gaps can be realized by allowing the at least partiallyuncured electrically insulating material to flow around the steppedcomponent assembly.

The wide recess can be seen as a wide shallow portion of the steppedcavity and the narrow recess can be seen as a deep narrow portion. Inthis consideration a part of the deep narrow portion it is locatedwithin the wide shallow portion of the stepped cavity.

In the context of this document the term “substantially completelycircumferentially surrounded” may denote that along the circumferentialdirection around the stepped component assembly there is a gap betweenthe stepped component assembly and an inner sidewall of the steppedcavity, which is filled by fully cured electrically insulating material.Thereby, the gap may extend fully around the stepped component assemblyand may be filled completely or partially (=substantially completely)with the fully cured electrically insulating material. In otherembodiments, a gap, which may at least partially be filled with thefully cured electrically insulating material may not extend completelyaround the stepped component assembly.

The term “circumferentially” may refer to a plane which is parallel withrespect to the main planes of the component carrier respectively thelayer stack. This means that the surfaces of the stepped componentassembly, which are in direct contact with the fully cured electricallyinsulating material, are side or lateral surfaces of the steppedcomponent assembly. Thereby, a side surface has a normal vector which isparallel to the main planes and perpendicular to a z-axis being orientedparallel to a normal vector of the main planes.

However, in this respect it is mentioned that the fully curedelectrically insulating material may not only be present lateral from ornext to the side surfaces of the stepped component assembly. The steppedcomponent assembly may also be embedded (along the vertical z-direction)at its upper side and/or at its lower side by fully cured electricallyinsulating material.

It is pointed out that the term “circumferentially surrounded” is not tobe understood as to refer only to a stepped component assembly which,along the z-direction, has a circular cross section. Instead,“circumferentially surrounded” may be understood in such a manner thatthe fully cured electrically insulating material may be present orencompass the stepped component assembly substantially completely alongthe (lateral) outline or length around the (upper and/or smaller)component of the stepped component assembly.

According to an embodiment of the invention the stepped componentassembly is substantially completely circumferentially surrounded by afurther fully cured electrically insulating material originating from atleast one other electrically insulating layer structure of the at leasttwo electrically insulating layer structures. This may mean that whenmanufacturing the component carrier, in particular by employing alamination procedure, not only one of the electrically insulating layerstructures but both of them must originally be in an at least partiallyuncured state.

In some embodiments, the fully cured electrically insulating materialmay be in contact predominantly or completely with one of the componentsof the stepped component assembly and the further fully curedelectrically insulating material may be in contact predominantly orcompletely with the other one of the components of the stepped componentassembly. Thereby, the spatial distribution between the fully curedelectrically insulating material and the further fully curedelectrically insulating material may be such that one of the twomaterials is exclusively and only in contact with only one of the twocomponents of the stepped component assembly.

Embedding the stepped component assembly with fully cured materialoriginating from different electrically insulating layer structures mayprovide the advantage that at least with respect to the (vertical)z-direction the stepped component assembly may be embedded in asymmetric manner which may further increase the reliability of anelectronic circuit comprising the stepped component assembly withrespect to (thermal) stress.

According to a further aspect of the invention there is described amethod of manufacturing a component carrier. The described methodcomprises (a) providing a layer stack comprising at least oneelectrically insulating layer structure and/or at least one electricallyconductive layer structure; (b) forming a stepped cavity within thelayer stack, the stepped cavity being defined by a narrow recess and bya wide recess, wherein the wide recess is formed by inserting anon-adhesive material in the layer stack and removing a portion of thelayer stack above the non-adhesive material; and (c) embedding a steppedcomponent assembly within the stepped cavity.

The described method is based on the idea that a stepped cavity can beformed by taking out a material piece from at least one layer of thecomponent carrier which material piece corresponds to one of the tworecesses. Thereby, an adhesion between two (electrically insulating)layer structures is intentionally reduced by the non-adhesive materialwhich is placed within a region which spatially corresponds to thebottom surface of the material piece. The non-adhesive material can beinserted into the proper position or location by way of a so-calledrelease layer being located on top of a layer structure which issupposed to be located directly below the respective recess (portion).

Before being able to take out the corresponding material piece it shouldbe ensured that the along a lateral direction the material piece isseparated from the material of the corresponding at least one layer ofthe component carrier. This can be done by cutting trenches within therespective component carrier layer, which trenches (fully) encompass thematerial piece being supposed to be taken out. Cutting trenches can bedone by mechanical and/or laser cutting or milling.

Also, in this aspect the wide recess can be seen as a wide shallowportion of the stepped cavity and the narrow recess can be seen as adeep narrow portion of the stepped cavity. In this consideration a partof the deep narrow portion it is located within the wide shallow portionof the stepped cavity.

It is pointed out that with this “release layer (RL) technique” not onlyone of the two recesses but both recesses of the stepped cavity can beformed. Thereby, in view of the stepped design of the cavity the area ofthe corresponding two release layers is different.

According to an embodiment of the invention the method further compriseselectrically connecting the stepped component assembly with conductivestructures formed within the layer stack by means at least one ofthermal compression bonding, soldering, and applying a conductive glue.This may provide the advantage that the electric contact to and/or fromat least one component of the stepped component assembly can be realizedsimultaneously with a proper lamination step.

Preferably, before the performing the described electrically connectingappropriate vertical via structures and/or horizontal conductor pathsmay have already been formed within the respective at least oneelectrically insulating structure and/or the at least one electricallyconductive layer structure. Thereby, also a rather complex electricwiring or circuitry can be used for electrically connecting the steppedcomponent assembly within the described component carrier. In thiscontext it is pointed out that after or together with a laminationprocess with which inter alia the electric connection to and/or from thestepped component assembly is realized, there may be furtherelectrically insulating layer structures and/or further electricallyconductive layer structures being attached to the layer stack. Thismeans that in a final product the described component carrier maycomprise one or more further built-up structures.

According to a further embodiment of the invention the method furthercomprises filling a gap between at least one component of the steppedcomponent assembly and an inner sidewall of the stepped cavity. The gapmay be in particular a gap being formed between a larger component ofthe stepped component assembly and an inner sidewall of the wide recess.

Inserting a filling or underfilling material within gaps being presentbetween the stepped component assembly and sidewalls of the steppedcavity may provide the advantage that the stepped component assembly canbe embedded in a smooth and mechanically reliable manner. Thereby, thenumber and/or the size of the gaps to be filled with (under)fillingmaterial can be chosen depending on the specific application of or forthe described component carrier.

It is pointed out that in particular an underfilling material may notonly be inserted within the side gap but also within a gap between ahorizontal surface portion of the stepped component assembly and acorrespondingly horizontal side wall of the stepped cavity. This mayprovide the advantage that at least one component of the steppedcomponent assembly cannot only be embedded along the lateral directionbut also along at least one vertical direction. This may further improvethe embedding quality.

According to a further aspect of the invention there is described acomponent carrier comprising (a) a layer stack comprising at least oneelectrically insulating layer structure and/or at least one electricallyconductive layer structure; (b) a stepped cavity within the layer stack,the stepped cavity comprising a narrow recess and a wide recess; and (c)a stepped component assembly embedded within the stepped cavity. Thestepped cavity comprises an undercut in a transition region between thenarrow recess and the wide recess.

The described component carrier is based on the idea that when a steppedcavity is formed within the component carrier by taking out a materialpiece from at least one layer of the component carrier, which materialpiece corresponds to one of two recesses, it is of advantage to make the(horizontal) area of a non-adhesive material layer at least slightlylarger than the horizontal area of the material piece to be taken out.Otherwise, there is a risk that a cut trench extending from the top downto the level of the non-adhesive material layer will not reach thenon-adhesive material. Such a horizontal offset would have the effectthat within a typically small horizontal region the cut out materialpiece would stick to the lower layer which may make taking out thatmaterial piece impossible or at least very difficult.

When, after having taking out the respective material piece thenon-adhesive material is removed from the region of the cavity, thenon-adhesive material being located laterally outside from therespective (narrow or wide) recess will also be removed at leastpartially although the material is covered by an upper layer structure(from which the material piece has been taken out). The removal of the(comparatively small portion of) non-adhesive material results in adeformation of the described undercut in the transition region betweenthe narrow recess and the wide recess.

According to an embodiment of the invention the narrow recess is athrough opening extending through the entire layer stack. Further, thecomponent carrier further comprises an adhesive film being formed at alower surface of the layer stack and closing the through opening.

The adhesive film formed at the bottom surface of the layer stack mayprovide the advantage that it allows for a subsequent insertion of afilling or underfilling material even when the narrow recess is realizedas a through opening. In this context it is mentioned that, as comparedto the formation of a blind opening, a through opening significantlyfacilitates the formation of the narrow recess and, as a consequence,also of the entire stepped cavity.

It is pointed out that the component carrier described with thisembodiment will typically represent an intermediate product for furtherprocessing the component carrier. Apart from inserting filling orunderfilling material in gaps between the stepped cavity and the steppedcomponent assembly the adhesive film may be used for performing anasymmetric lamination wherein, apart from the described layer stack andwith respect to the surface at which the adhesive film is formed, afurther built-up structure can be formed at an opposing surface of thelayer stack. Thereby, the adhesive film may be seen as to represent atemporary carrier for the layer stack.

According to a further embodiment of the invention the stepped componentassembly comprises a stack of at least two components having a differentsize and/or a different functionality. Thereby, a first (upper)component may be smaller and/or may have a smaller lateral extensionthen a second (lower) component of the stepped component assembly.

The two components may be electronic components which are electricallyconnected with each other. Thereby, the two components may be arrangedface to face being directly connected with each other by means of anysuitable contact structure, for instance solder balls.

The two components may also be connected indirectly with each other forinstance by means of an intermediate electronic component orintermediate electronic structure. Thereby, the intermediate electronicstructure may be seen as one component of the stepped componentassembly, in particular when the size respectively the lateral extensionof the intermediate electronic structure is different from the firstelectronic component and/or the second electronic component. In thiscase the stepped electronic assembly comprises three components. In caseall of the three components have different sizes respectively lateralextensions the stepped component assembly has an outer shape with twosteps. In this respect it is mentioned that there is no principalmaximum number for the number of components being comprised by thestepped component assembly.

The intermediate electric structure may be an IC substrate or aninterposer. The substrate or interposer may consist of at least a layerof glass, Silicon (Si) or a photoimageable or dry-etchable organicmaterial like epoxy-based Build-Up films or polymer compounds likePolyimide, Polybenzoxazole, or Benzocyclobutene.

In some applications the intermediate electric structure may be a PCBlike structure having a high spatial density of vertical electricconnections wherein neighboring electric connections have an averagedistance or at least a distance in some sections of the intermediateelectric structure of less than 150 μm and preferably less than 75 μm.The same spatial distances or even smaller distances are given for aninterposer or a substrate having the two electronic components mountedthereto at opposing surfaces of the interposer or substrate. Inpreferred embodiments the high integration density of electricconnections is realized with an interposer or a substrate being freefrom typical materials for electrically insulating layer structures ofPCBs comprising glass fibres like FR4 material. Thus, an even higherdensity of connections is possible wherein the neighboring verticalelectric connections may have a distance in some sections of theintermediate electric structure of less than 30 μm and preferably lessthan 15 μm. Ultra-high-density electric connections between the at leasttwo components having a distance of the neighboring vertical electricconnections in some sections of the intermediate electric structurebelow 5 μm may be realized by means of so called “Through-Silicon Vias”.

In most preferred embodiments the two components are horizontallyaligned with respect to a vertically oriented symmetry axis. Withrespect to this symmetry axis and/or with respect to a symmetry planecomprising the symmetry axis the stepped component assembly issymmetric. The same holds mutatis mutandis also for the spatial designof the stepped cavity.

According to a further embodiment of the invention the component carrierfurther comprises at least one contact element extending from the largercomponent to a surface of the component carrier and penetrating a layerstructure of the layer stack within which the narrow recess is formed.

This may mean that at least one contact element is located horizontallynext to the smaller component of the stepped component assembly. In casean upper surface of the smaller component is coplanar with an uppersurface of the component carrier the contact element reaches the surfaceof the component carrier at the same side as the upper surface of thesmaller component. This may be in particular of advantage for a sensorapplication because the sensing component carrier can be contacted fromthe outside at its “sensitive side”.

The mentioned contact element may be realized by means of or maycomprise for instance a metallized via or a stack of metallized vias.

According to a further embodiment of the invention the component carriercomprises at least one of the following features: (a) at least one ofthe two components is a sensor component; (b) an upper surface ofcomponent assembly is coplanar with an upper surface of the layer stack;(c) one (upper) component is or comprises a protection element; and (d)one (upper) component is or comprises an optical lens.

With regard to the embodiment (a) where at least one of the twocomponents is a sensor component:

Depending on the intended functionality of application the sensorcomponent may be an optoelectronic sensor, a gas sensor, a temperaturesensor, a magnetic field sensor, an electric field sensor etc.Preferably, the sensor is realized by this (electronic) component of thestepped component assembly, which component is the smaller one. Theother larger electronic component may be used for processing and/or forevaluating measurement signals provided by the sensing sensor componentand/or for providing electric power to the sensor component.

Depending on the specific application a sensing surface of the sensorcomponent may be located outside from the component carrier or may belocated recessed within the component carrier or the layer stack.Arranging the sensing surface outside from the layer stack may providethe advantage that the environment of the component carrier can besensed easily. Arranging the sensing surface within a recess (being apart of the stepped cavity) may provide the advantage that the sensorcomponent is protected from unwanted (mechanical) impacts acting on thecomponent carrier. Such a protection can be increased by means of asuitable protection material, e.g. a transparent mold, being formedwithin the recess and/or over the sensing surface.

With regard to the embodiment (b) where an upper surface of componentassembly is coplanar with an upper surface of the layer stack:

The upper surface may form a flat plane together with the correspondingsurface of the component carrier or the layer stack. Embodiments wherethese two surfaces form a common flat surface of the component carriermay allow to design an electronic device with the component carrierrepresenting at least a portion of a housing of this electronic device(comprising the component carrier) in such a manner that the steppedcomponent assembly is integrated within the component carrier withoutbeing visible from outside.

The described coplanar design may be in particular of advantage in casethe (upper) component of the stepped component assembly is a sensorcomponent. In such cases the upper component of the stepped componentassembly has a surface which is arranged within the same plane as theupper surface of the layer stack. Further advantage may be taken fromsuch embodiments when the sensor component comprises a sensing surfacebeing located within the plane of the corresponding outer surface of thecomponent carrier.

With regard to the embodiment (c) where one (upper) component is orcomprises a protection element:

This may provide the advantage that (the upper surface of) the steppedcomponent assembly can be protected from external impacts. This may bein particular of advantage in case the protected surface of the steppedcomponent assembly it is a sensing surface of a sensor component.

With regard to the embodiment (d) where one (upper) component is orcomprises an optical lens:

Providing an optical element such as a lens may be of advantage in casethe sensor component is an optically sensor. In this case light can befocused on the sensing surface of the optical sensor component. It ismentioned that such an optically component may also make sense in casethe (upper) component of the stepped component assembly is a lightsource such as a light emitting diode or a laser diode embedded withinthe component carrier. Depending on the space being necessary and/orbeing available, the optical element may be a so-called micro-lens whichmay be realized by forming, e.g. by means also molding procedure, atransparent resin within the stepped cavity. A lens may also be formedin between a protection element and an upper surface of the (upper)component of the stepped component assembly.

It has to be noted that embodiments of the invention have been describedwith reference to different subject matters. In particular, someembodiments have been described with reference to method type claimswhereas other embodiments have been described with reference toapparatus type claims. However, a person skilled in the art will gatherfrom the above and the following description that, unless otherwisenoted, in addition to any combination of features belonging to one typeof subject matter also any combination between features relating todifferent subject matters, in particular between features of the methodtype claims and features of the apparatus type claims is considered asto be disclosed with this document.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G to 1H illustrate a manufacturing of acomponent carrier with an embedded stepped component assembly, wherein atemporary carrier is employed.

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 2I, 2J, 2K, 2L, 2M, 2N, to 2Oillustrate a manufacturing of two component carriers wherein, with thehelp of a release layer, a wide recess of a stepped cavity is formed,into which a stepped component assembly is embedded.

FIG. 3 illustrates the formation of an undercut when removing a releaselayer which has been used for forming a wide recess of a stepped cavity.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

The aspects defined above and further aspects of embodiments of theinvention are apparent from the examples of embodiment to be describedhereinafter and are explained with reference to the examples ofembodiment. The invention will be described in more detail hereinafterwith reference to examples of embodiment but to which the invention isnot limited.

The illustrations in the drawings are schematically presented. It isnoted that in different figures, similar or identical elements orfeatures are provided with the same reference signs or with referencesigns, which are different from the corresponding reference signs onlywithin the first digit. In order to avoid unnecessary repetitionselements or features, which have already been elucidated with respect toa previously described embodiment, are not elucidated again at a laterposition of the description.

Further, spatially relative terms, such as “front” and “back”, “above”and “below”, “left” and “right”, et cetera are used to describe anelement's relationship to another element(s) as illustrated in theFigures. Thus, the spatially relative terms may apply to orientations inuse which differ from the orientation depicted in the Figures.Obviously, all such spatially relative terms refer to the orientationshown in the Figures only for ease of description and are notnecessarily limiting as an apparatus according to an embodiment of theinvention can assume orientations different than those illustrated inthe Figures when in use.

FIGS. 1A to 1H illustrate the manufacture of a component carrier 100with a stepped component assembly 160 being embedded within a steppedcavity 150 of a layer stack of the component carrier 100.

As can be seen from FIGS. 1A and 1B, the manufacturing process startswith preparing a layer composite or layer stack 110, wherein a copperfoil 113 representing an electrically conductive layer is laminated on aprepreg layer 112 representing an (uncured) electrically insulatinglayer. Thereby, it is ensured that the temperature during thislamination process is kept below the polymerization temperature of(epoxy) resin being comprised in the prepreg layer 112. In this case the(uncured) resin escapes partially from the prepreg layer 112 andconnects to the (lower) treatment surface of the electrically conductivelayer 113. Thereby, the electrically insulating layer remains at leastpartially uncured.

In a next step illustrated with FIG. 1C, a through opening is formedwithin the layer stack 110. Thereby, the opening within the electricallyconductive layer 113 is denominated with reference numeral 113 a and theopening within the electrically insulating layer 112 is denominated withreference numeral 112 a. Further, not illustrated in FIG. 1C, fiducialscan be formed in particular at the lower surface of the electricallyinsulating layer 112.

In a next step illustrated with FIG. 1D, a temporary carrier 105 islaminated on top of the layer stack 110. The temporary carrier 105 maybe realized simply with an adhesive film. Further, a portion of thestepped component assembly 160 is inserted in a narrow recess 152, whichcorresponds to the openings 112 a and 113 a described above. In theembodiment described here the second component is an optical sensorcomponent 164 having an upper sensing surface which is (mechanically)protected by the first component 162 representing a protection element.In order to improve the “optical rate of yield” a light ray guidingelement being a micro-lens 166 may be optionally arranged in between theprotection element 162 and the optical sensor component 164. In thiscontext it should be clear that the protection element 162 should betransparent at least for spectral components of light which are supposedto be detected by the sensor component 164.

The protection element 162 could be a glass plate, in particular if theoptical sensor component 164 is a camera sensor. The glass plate may beseparated from the surface of the camera sensor by an air gap in orderto allow for a correct refraction. Using a glass plate as the protectionelement 162 may provide the advantage that the protection element 162will withstand a following PCB production processes like a structuringprocess, a solder mask process, and an assembling process. Further, theglass plate may protect a sensible sensor surface during theseprocesses.

The component assembly 160 may be a pre-assembled structure which meansthat the two components are attached to each other before mounting themto the layer stack 110. Alternatively, first the first component 162 maybe placed into the narrow recess 152 and second the second component 164is mounted at the bottom surface of the first component 162.

In order to mount either the entire component assembly 160 or the twoindividual components 162, 164 of the component assembly 160 in aspatially precise manner the above described fiducials may be used.Mounting can be carried out with any usual (automated) mounting process.

It is mentioned that in other embodiments the stepped component assemblymay comprise two electronic components, a first small or narrow uppercomponent and a second bigger or wide lower component, which arearranged face to face with respect to each other. Thereby, non-depictedelectric contacts of the two components may be electrically connectedwith each other by means of a contact structure which may beschematically illustrated with the reference numeral 166 (correspondingto the micro-lens of the embodiment actually shown in the drawing). Sucha contact structure may be realized for instance by means of aninterposer which ensures that the contacts of the first component areconnected with the contacts of the second component in a proper electricmanner.

Turning back to the embodiment illustrated in the drawing. As can befurther seen from FIG. 1D, according to the embodiment described here anupper surface portion of the second electronic component 164, whichupper surface portion is not covered by the first electronic component162, is provided with a contact pad 168. In further processing stepsthis contact pad 168 can be used to directly contact the second sensorcomponent 164 with external circuitry being arranged above the layerstack 110.

In a next step illustrated with FIG. 1E, further layer structures arearranged at the bottom side of the prepreg layer 112 respectively at thelower surface of the second component 164.

(A) Specifically, first a pre-assembled sandwich structure comprisingtwo electrically conductive layers 123 and one electrically insulatinglayer 122 in between is arranged at the prepreg layer 112. Thispre-assembled sandwich structure comprises an opening which spatiallycorresponds to the size and the shape of the second component 164.According to the embodiment described here the thickness of thispre-assembled sandwich structure is substantially the same as thethickness of the second component 164. The opening within thepre-assembled sandwich structure (later) corresponds to a wide recess154 of the stepped cavity 150.

As can be seen from FIG. 1E, the opening within the pre-assembledsandwich structure 122, 123 is slightly larger respectively wider thanthe second component 164. This means that in between an outer sidewallof the second component 164 and an inner sidewall of the recess 154there is formed a gap 156.

(B) Second, a further electrically insulating layer 124 together with afurther electrically conductive layer 125 is arranged at the bottom sideof the pre-assembled sandwich structure having the opening for thesecond component 164. According to the embodiment described here, due tothe basically same thicknesses of (i) the second component 164 and (ii)the pre-assembled sandwich structure both the further electricallyinsulating layer 124 and the further electrically conductive layer 125do not have such an opening.

In a next step illustrated with FIG. 1F, the entire structure shown inFIG. 1E is laminated. Thereby, due to lamination heat and/or laminationpressure at least partially uncured electrically insulatingmaterial/resin originating from the prepreg layers 112 and 124 liquefiesand enters the gaps 156. The corresponding material flows aredenominated with reference numeral M. Optionally, at least partiallyuncured resin may enter further gaps formed between the outer sidewallsof the first component 162 and the inner sidewalls of the narrow recess152.

In a next step illustrated with FIG. 1G the temporary carrier 105 isremoved. The remaining layer stack having the stepped component assembly160 embedded is denominated with reference numeral 130.

It is pointed out that apart from protecting in particular the firstcomponent 162 from external physical and/or chemical impacts during theprocess steps elucidated above the temporary carrier 105 has the effectthat the upper surface of the first component 162 and the upper surfaceof the layer stack 110 are coplanar. This means that the first component162 will neither protrude from the layer stack 110 nor will form (thebottom surface of) a recess within the layer stack 110.

In a next (last) step illustrated with FIG. 1H (i) the upperelectrically conductive layer and the lower electrically conductivelayer are structured in order to form appropriate conductor paths (notshown in FIG. 1H) and (ii) contact elements 169 are formed in order toelectrically contact the second component respectively the opticalsensor component 164 with external circuitry. According to theembodiment described here the contact elements 169 are metallized viasextending through the layer stack 110. This means that the opticalsensor component 164 is electrically contacted from the upper side.Thereby, the upper side is the light sensitive side of the componentcarrier 100 having the stepped component assembly 160 embedded in such amanner that the upper surface of the protection element 162 does notprotrude outwardly from (the layer stack 110 of) the layer stack 130.

Optionally, after having completed all steps illustrated above theprotection element 162, which it is located above the sensing surface ofthe optical sensor component 164, can be removed. Such a removal may benecessary if the protection element 162 blocks the light which issupposed to be detected by the sensor component 164. This removal may berealized by means of plasma etching, a wet chemical procedure, and/or amechanical procedure. Further, laser cutting may be employed in order tocut out a material piece of the protection element 162. When applyinglaser cutting it may be beneficial to provide a so-called laser stoplayer in between the sensing surface of the second component 164 and thelower surface of the protection element 162. With such a laser stoplayer, which may be simply a copper layer, an unintended damaging of thesensing surface may be prevented. In some embodiments, which arecurrently considered as to the present preferred embodiments, theprotection element 162 may be an adhesive film which is durable againstany impact acting on the sensing surface of the sensor component 164during all process steps. After completing the manufacturing of thedescribed component carrier 100 this adhesive film may simply be pulledoff.

FIGS. 2A to 2L, and 2M illustrate a method of manufacturing a componentcarrier 200 a wherein, with the help of a release layer, a wide recessof a stepped cavity is formed, into which an upper larger component of astepped component assembly is embedded. FIGS. 2A to 2L, 2N, and 2Oillustrate a method of manufacturing a further and similar componentcarrier 200 b. FIGS. 2A to 2L apply to the manufacturing of bothcomponent carriers.

As can be seen from FIG. 2A, first there is provided a sandwichstructure comprising an uncured electrically insulating layer or prepreglayer 212 which is sandwiched between two electrically conductive layers213. Each one of the two electrically conductive layers may be realizedby one metallic (copper) foil 213.

In a next step illustrated with FIG. 2B, both electrically conductivelayers 213 are structured. Further, appropriate contact structures 270extending through the prepreg layer 212 are formed. The structuring iscarried out in such a manner that in a central region of bothelectrically conductive layers 213 the electrically conductive (copper)material is removed completely such that a comparatively large openingis formed within each layer 213. As will be seen from the Figuresdescribed below in detail, the shape and the size of the openings of thetwo layers 213 correspond to a narrow recess of a stepped cavity. Theformation of the contact structures 270 may be realized in a knownmanner by means of metallized vias. Since a formation of such vias 270is well known to the skilled person no further details are presented inthis document.

In a next step illustrated with FIG. 2C, a non-adhesive material 280 isformed as a layer over the upper structured electrically conductivelayer 213 such that the opening within this layer 213 is fully covered.Further, along a horizontal direction the non-adhesive material 280,which represents a so-called release layer 280, has a significantlywider extension than this opening.

In a next step illustrated with FIG. 2D, a further layered structurecomprising an electrically insulating or prepreg layer 222 as well as afurther electrically conductive layer 213 are laminated on top of therelease layer 280 (and the structured electrically conductive layer213). Further, a (new) layered structure comprising an electricallyinsulating or prepreg layer 212 as well as a further electricallyconductive layer 213 are laminated at the bottom of the layer structureof FIG. 2C.

In a next step illustrated with FIG. 2E, the now topmost electricallyconductive layer 213 and the lowermost electrically conductive layer 213are structured. Thereby, the topmost electrically conductive layer 213is provided with an opening (i) having the same shape and almost thesame size as the release layer 280 and (ii) corresponding to a widerecess of the stepped cavity mentioned above. The lowermost electricallyconductive layer 213 is provided with an opening having a geometry whichcorresponds to a narrow recess of this stepped cavity.

Further, as can also be seen from FIG. 2E, some further electric viaconnections 270 are formed. According to the embodiment described heretwo “new” electric via connections 270 (depicted in FIG. 2E top left andbottom right) are formed and two via connections 270 extend alreadypreviously formed via connections penetrating the electricallyinsulating layer 212, which layer 212 is located directly below therelease layer 280.

Next, as illustrated with FIG. 2F, the previous steps illustrated withFIGS. 2D and 2E are carried out again in an analogous manner. This meansthat (i) at the top a further upper electrically insulating layer 222and a further upper electrically conductive layer 213 with an openingcorresponding to the wide recess is formed and (ii) at the bottom afurther lower electrically insulating layer 212 and a further lowerelectrically conductive layer 213 with an opening corresponding to thenarrow recess is formed. Further, a new via connection is formed(depicted in FIG. 2F top right) and other already existing viaconnections are extended such that further extended stacked viaconnections 270 are produced.

FIG. 2G illustrates the result of two following steps, wherein again (i)at the top an additional upper electrically insulating layer 222 and anappropriately structured additional upper electrically conductive layer213 is formed and (ii) at the bottom an additional lower electricallyinsulating layer 212 and an appropriately structured additional lowerelectrically conductive layer 213 is formed. Further, additional viaconnections are formed which extend already existing stacked viaconnections 270. Now, a layer stack has been formed, which isdenominated with reference numeral 210. This layer stack 210, which canbe seen as to represent a core which has been produced by subsequentsteps of laminating, structuring, and via forming, is the starting pointfor the formation of a stepped cavity.

Next, as illustrated with FIG. 2H, a narrow and deep recess 252extending completely through the layer stack 210 is formed. Theformation of the recess 252, which can be seen as to represent a throughhole, can be carried out by means of (mechanical) milling or lasercutting.

Next, as illustrated with FIG. 2I, a wide and shallow recess 254 isformed above the release layer 280. Thereby, a material piece is takenout from the upper electrically insulating layers 222 (as well as fromthe upper electrically conductive layers 213). According to theembodiment described here the described material piece is cut out bymeans of a laser cutting procedure. In a non-depicted top view thecorresponding laser beam defines a closed laser cutting lineencompassing the material piece. The laser cut extends from the top ofthe layer stack 210 down to the release layer 280. Thereby, thestructured electrically conductive (copper) layer 213 formed directlybelow the release layer 280 acts as a laser stop layer. After cuttingout this material piece in the described manner the material piece istaken out from the layer stack 210. Further, the remainders of therelease layer 280 are removed, e.g. by means of a known strippingprocedure.

For process reliability reasons the release layer 280 is, along ahorizontal direction, slightly larger or wider than the wide recess 254.This has the effect that when completely removing the release layer 280there is formed a (small) undercut 254 a.

Next, as illustrated with FIG. 2J, a stepped component assembly 260comprising a (bottom) first (small) component 262 and an (upper) second(large) component 264 is inserted into a stepped cavity 250 (mentionedalready above) being defined by the narrow recess 252 and the widerecess 254. At the bottom surface of the second component 264 in asurface portion being not covered by the first component 262, there areformed contact pads 268 which can be used for electrically connectingthe component 264 (from its bottom side) with external circuitry. Thesecontact pads 268 are electrically connected to corresponding connectionportions of the structured electrically conductive layer 213, which isthe most upper electrically conductive layer of the layer stack beingassigned to the narrow recess 252. The electric connection between thecontact pads 268 and these connection portions can be realized inparticular by means of a thermal compression bonding which may becarried out in the absence of any lamination step. Alternatively, thiselectric connection can also be realized by means of soldering and/orgluing with an electrically conductive glue.

As can be seen from FIG. 2J, the lateral or horizontal extension of thestepped cavity 250 is slightly larger than the lateral extension of thestepped component assembly 260. Therefore, after inserting the steppedcomponent assembly 260 there are formed gaps 256 in between the outerside or lateral surfaces of the stepped component assembly 260 and thecorresponding inner sidewalls of the stepped cavity 250.

Next, as illustrated with FIG. 2K, an adhesive layer or film 207 isattached at the most bottom surface of the layer stack 210.

Next, as illustrated with FIG. 2L, the gaps 256 are at least partiallyfilled with a filling or underfilling material 257 which in thedescribed embodiment is inserted from above. It is mentioned that suchan (under)filling material 257 may also be taken from presently at leastpartially uncured prepreg layers and/or may be inserted from the bottombefore the adhesive film 207 has been attached. From FIG. 2L it can befurther seen that according to the embodiment described here the(under)filling material 257 did not enter the undercuts 254 a such thatthere remain unfilled voids 254 b.

FIG. 2M illustrates the last process step for manufacturing thecomponent carrier 200 a. In this last process step the adhesive film 207is removed.

In preferred embodiments the first component is an optical sensorcomponent 262 having its sensing surface at the bottom. Therefore, whenremoving the adhesive film 207 the sensing surface of the optical sensorcomponent 262 is exposed and “ready to sense”.

FIG. 2N and FIG. 2O illustrate the last process steps for manufacturingthe component carrier 200 b. As can be taken from FIG. 2N, after fillingthe gaps 256 with (under)filling material 257 (see FIG. 2L) a furtherlayered structure comprising an electrically insulating or prepreg layer222 as well as a further electrically conductive layer 213 are laminatedon top of the layer stack 210. Further, a new via connection 270 isformed (depicted in FIG. 2N top right) and other via connections areextended such that further extended stacked via connections 270 areformed. FIG. 2O illustrates the last process step for manufacturing thecomponent carrier 200 b. In this last process step the adhesive film 207is removed.

It is mentioned that filling the gaps 256 with (under)filling material257 can also be accomplished by means of a vacuum lamination. In thiscase an upper laminate layer is formed under vacuum above the secondcomponent 264. Also, this upper laminate layer may comprise anelectrically insulating prepreg layer and an electrically conductive(copper) layer above this prepreg layer.

It is further mentioned that embodiments of the invention may comprise asimultaneous embedding of at least two stepped component assemblieswithin at least two corresponding stepped cavities. Thereby, amulti-sensor device can be realized by an easy processing of well-knownPCB materials and structures.

Furthermore, it is mentioned that the described embedding of a steppedcomponent assembly within a stepped cavity allows to mount the steppedcomponent assembly according to the principle of “chip-last”. This mayallow to fully test the functionality of the stepped component assemblybefore embedding it with the procedures and steps described in thisdocument.

FIG. 3 illustrates the formation of an undercut when (completely)removing the release layer 280 which has been used for forming the widerecess 254 of the stepped cavity 250.

As has been already mentioned above, along a lateral or horizontal x- ory-direction the release layer 280 has a larger extension than a materialpiece which is cut out from at least one electrically insulating layer222. The lateral extension of the material piece is defined by theposition of a (closed) cutting line 355 which could best be seen in atop view along a vertical z-direction. When taking out this materialpiece the wide recess 254 is formed. It should be clear from FIG. 3 thatwhen removing or stripping off the release layer 280 there will beformed the above mentioned undercut within an undercut region depictedin FIG. 3 with reference numeral 355.

It should be noted that the term “comprising” does not exclude otherelements or steps and the use of articles “a” or “an” does not exclude aplurality. Also, elements described in association with differentembodiments may be combined.

LIST OF REFERENCE SIGNS

-   100 component carrier-   105 temporary carrier-   110 layer stack-   112 electrically insulating layer (uncured)/prepreg layer-   112 a opening-   113 electrically conductive layer/metallic foil/copper foil-   113 a opening-   122 electrically insulating layer/prepreg layer with opening-   123 electrically conductive layer/metallic foil/copper foil-   124 further electrically insulating layer-   125 further electrically conductive layer/metallic foil/copper foil-   130 layer stack-   150 stepped cavity-   152 narrow recess-   154 wide recess-   156 gap-   160 stepped component assembly-   162 first component/protection element-   164 second component/optical sensor component-   166 light ray guiding element/micro-lens-   168 contact pad-   169 contact element/metallized via-   M material flow-   200 a component carrier-   200 b component carrier-   207 adhesive layer/adhesive film-   210 layer stack-   212 electrically insulating layer (uncured)/prepreg layer-   213 electrically conductive layer/metallic foil/copper foil-   222 electrically insulating layer/prepreg layer-   250 stepped cavity-   252 narrow recess-   254 wide recess-   254 a undercut-   254 b void-   256 gap-   257 (under)filling material-   260 stepped component assembly-   262 first component/optical sensor component-   264 second component-   268 contact pad-   270 contact structure/contact element/(stacked) metallized via(s)-   280 non-adhesive material/release layer-   354 c region of undercut-   355 cutting line

The invention claimed is:
 1. A method of manufacturing a componentcarrier, the method comprising: providing a temporary carrier;providing, attached to the temporary carrier, an at least partiallyuncured electrically insulating layer structure having a narrow recess;providing a layer stack comprising at least one electrically insulatinglayer structure and/or at least one electrically conductive layerstructure, the layer stack having a wide recess; arranging a steppedcomponent assembly at least within the narrow recess; and connecting theat least partially uncured electrically insulating layer structure withthe layer stack by curing the at least partially uncured electricallyinsulating layer structure such that the stepped component assembly isarranged within a stepped cavity being defined by the narrow recess andby the wide recess.
 2. The method as set forth in claim 1, wherein atleast one electrically insulating layer structure of the layer stackcomprises a further at least partially uncured electrically insulatinglayer structure.
 3. The method as set forth in claim 1, furthercomprising: after arranging the stepped component assembly within thestepped cavity and before connecting the at least partially uncuredelectrically insulating layer structure with the layer stack, laminatingthe entire structure comprising the temporary carrier, the at leastpartially uncured electrically insulating layer structure, and the layerstack in such a manner that at least partially uncured electricallyinsulating material flows at least partially around the steppedcomponent assembly.
 4. The method as set forth in claim 1, furthercomprising: removing the temporary carrier from the connected structurecomprising the previously at least partially uncured electricallyinsulating layer structure and the layer stack.
 5. The method as setforth in claim 1, further comprising: providing a single electricallyconductive layer structure between (i) the temporary carrier and (ii)the at least partially uncured electrically insulating layer structurehaving the narrow recess, wherein in particular the single electricallyconductive layer structure has an opening being spatially concurrentwith the narrow recess.
 6. A method of manufacturing a componentcarrier, the method comprising: providing a layer stack comprising atleast one electrically insulating layer structure and/or at least oneelectrically conductive layer structure; forming a stepped cavity withinthe layer stack, the stepped cavity being defined by a narrow recess andby a wide recess, wherein the wide recess is formed by inserting anon-adhesive material in the layer stack and removing a portion of thelayer stack above the non-adhesive material; and embedding a steppedcomponent assembly within the stepped cavity.
 7. The method as set forthin claim 6, further comprising: electrically connecting the steppedcomponent assembly with conductive structures formed within the layerstack by means at least one of thermal compression bonding, soldering,and applying a conductive glue.
 8. The method as set forth in claim 7,further comprising: filling a gap between at least one component of thestepped component assembly and an inner sidewall of the stepped cavity,in particular a gap between a larger component of the stepped componentassembly and an inner sidewall of the wide recess.